1. Field of the Invention
The present invention relates to an apparatus for connecting a remote viewer (such as binoviewer or camera) to a telescope, and more specifically, a modular, multi-purpose, optical system that can be used with several different types of telescopes, which brings the focal plane of the telescope out to the remote viewer without requiring altering of the telescope, and without excessive magnification.
2. Description of the Prior Art
The use of a telescope for viewing astronomical objects such as stars and nebulae is conventionally undertaken with one eye. Accordingly, the design of any particular type of telescope is usually optimized for this type of viewing. In Newtonian Telescopes, “Optimization” refers to configuring the optical components of the telescope so that aberrations are minimized. The result of this optimization is that the focal plane created by the optical components, such as the primary and secondary mirrors, will fall at a point within the focusing tube where a single eyepiece may intercept and create an image, which may then fall upon the viewer's retina so that a user of the telescope can see the image. However, if a remote viewing accessory such as a binocular viewer (hereinafter called a “binoviewer”) is placed in the focusing tube, and eyepieces are then placed in the binoviewer, these eyepieces will be as much as 150 mm further from the focal plane created by the optical components of the telescope.
In the prior art, in an attempt to correct for this, a single tele-negative lens (sometimes called a relay or Barlow lens) system, was used so that the focal length of the optical system inherent to that particular telescope would be increased. Since the tele-negative system could intercept the light cone and then increase the distance where the light cone terminates in the form of a focus, this “increased distance” focal plane can now be intercepted by the eyepieces that are placed in a binoviewer. However, there is a serious price to be paid with this prior art technique. That is, because a tele-negative lens produces a more slowly converging light cone, the longer the light cone traveled after passing through the telenegative lens, the more of an increase in magnification will occur. Thus, the use of a tele-negative lens alone in order to adapt the focusing ability to a remote viewing device such as a binoviewer would create very high magnification, even if low power eyepieces are used in the binoviewer. Since many astronomical objects are best viewed with low power because of their large size and low surface brightness, the lack of this low power viewing option restricted the use of a binoviewer to viewing brighter objects where high power was desirable such as The Moon or Planets.
Although it is also known that a positive lens could be used in conjunction with a housing that holds the tele-negative lens, such a technique results in a light path correction component that is unique and unchangeable for the particular telescope it is designed to work with. Quite often amateur astronomers have more than one type of telescope, and it would be desirable that their binoviewer be adaptable for use/operation with their other telescopes. Additionally, it would be desirable that the binoviewer be able to provide different levels of image magnification.
One option used in the prior art to counteract this magnification effect in a Newtonian (reflecting) telescope is to decrease the distance between the primary mirror and the secondary mirror. This can be accomplished in several ways, however, when this is done by any means, the secondary mirror must then reflect the converging light cone reflected from the primary mirror at a point where this light cone is wider. Therefore, the use of a larger secondary must be implemented or else the true used aperture of the primary will be reduced. Since the cost of primary mirrors is increased exponentially with diameter, this is not a commonly acceptable solution. Additionally, if the size of the secondary mirror is increased so that the entire primary is utilized, then aberrations due to the larger secondary obstruction are introduced. Even furthermore, the single eyepiece on the telescope would also require the use of an extension tube in order that it can reach focus in such a modified telescope, due to the increased back focus caused by the decreased distance between the primary and secondary mirrors. Relocating the weight of the eyepieces to a more outward location on the binoviewer creates difficulty in balancing the telescope, and is detrimental to maintaining an ease of use of such a reconfigured telescope. Therefore this solution is also considered unsatisfactory by those familiar in the art of astronomy.
With Refracting telescopes, the ability to reach focus when using an added binoviewer may not be possible, due to the conventional use of a star diagonal optical system. The star diagonal is conventionally used with a Refracting telescope since it allows the user to view the image created by the telescope at a comfortable position/angle. Although Refracting telescopes are generally configured to allow for the extra light path caused by the use of a star diagonal, their configuration generally does not allow for the even greater light path which results when a binoviewer is added after the star diagonal. Accordingly, when a binoviewer is used with a Refractor telescope having a star diagonal, an optical corrector system would be needed to compensate for this additional back focus requirement. One solution in the past has been to use the binoviewer without a star diagonal, that is, by attaching the binoviewer directly in line with the telescope lenses (however, most Refractors still cannot bring the focal plane out to the eyepieces of a binoviewer even in the absence of a star diagonal). Even if the focus requirement was met, although this technique may be satisfactory for viewing objects very low on the horizon, it would still provide an unsatisfactory viewing position/angle for viewing anything higher than 30-40 degrees above the horizon. Since it is known that the steadiest atmospheric conditions occur higher than 45 degrees from the horizon, this solution is also not acceptable. Because Refractor type telescopes are very expensive, and owners of such instruments are concerned with resale value, a second solution which involves physically shortening the length of the refractor tube is also not an acceptable solution. Even furthermore, if the focuser tube of a Refracting telescope were placed closer to the objective lens by shortening the tube length of the telescope, the converging peripheral rays created by the primary objective could also vignette or be cut off by the focuser. Refractors with fast focal ratios may be especially susceptible to this possibility due to the steep convergence of such a light cone.